This invention relates to an electric strike that is small enough to be used in multiple applications and can be configured in the field for fail-safe or fail-secure operation.
The field of electrically operated strikes is filled with a multitude of devices, which essentially do the same thing: they release a latch that extends into the body of the strike so as to open the door that contains the latch. They commonly use a solenoid which, through some mechanical linkage, will release the keeper holding the latch and then return to its locked condition after the latch is released. There are very few electric strikes whose keeper extends into a latch contained within the door and, upon energizing, not only rotates out of the latch, but also remains in its rotated condition until the door closes and the latch returns the keeper to its locked condition. For reference there are two such devices: an electric strike disclosed in U.S. Pat. No. 5,076,625 issued to Oxley on Dec. 31, 1991; and an electric strike called the Panicloc (trademark), formerly manufactured by SDC, Inc., of Westlake Village, Calif., USA.
The present invention is designed to control the most widely used concealed vertical rod exit devices that come as standard equipment on aluminum storefront type doors such as those made by the Dor-O-Matic Company, of Harwood Heights, Ill., USA. This exit device has been the largest selling exit device in the world, and yet, it has been the most difficult to adapt to electronic access control systems because it features a unique latching system. A U-shaped latch is mounted in the top of the door and does not extend beyond the outer edge of the door. A pin, which is mounted on the header, engages the latch. When the exit device is operated from the inside, the latch releases by the movement of the push bar, and the motion of the opening door forces the latch to pivot via the pin on the header. The pin then passes through a slot in the inside skin of the door as it opens. When the door closes, the header pin contacts the latch and rotates it back to its vertical (locked) position. As computerized access control becomes more necessary, more of these OEM devices will need to be controlled. The present invention provides a cost-effective solution to the drawbacks of the prior art devices. Additionally, since the adoption in the United States of the Americans with Disabilities Act, and similar legislation in other countries, a great many more of these existing doors need to be retrofitted with automatic door openers that require an electric strike to release the door.
The existing device referenced is the electric strike identified by U.S. Pat. No. 5,076,625. It features a keeper shaped with a lobe that extends into the U-shaped latch and swings out of the way when the strike is energized and the door is opened. That strike, in its preferred embodiment, is built on an existing electric strike body available from an established manufacturer to take advantage of a proven “platform” upon which to build. This was done to speed the product to market and avoid the costly task of making the strike from scratch. The “platform” strike is asymmetrically designed relative to where the keeper is placed in the body of the strike. This characteristic limits the useful application of the strike to include only a few possible applications. Additionally, the strike malfunctions after a particular combination of events occurs. When an authorized individual gains access, the strike is energized by the access control system. The motion of the door opening rotates the keeper out of the latch. Normally, the door closes, rotating the keeper back and re-locking it after the person has entered. If, however, the panic bar is pushed before the door closes, (for example if another person exits just after the entry is achieved), the latch rotates toward the inside of the door and hits the keeper as it tries to rotate back to its closed position. This causes an interference that keeps the door from closing and locking. There are also difficulties one encounters while installing the strike. The design of the platform strike situates the body of the strike behind the outside edge of the doorstop. Proper installation requires the installer to measure over the door stop “rib” in the header and lay out lines for the cutout needed to mount the strike. This proves to be difficult for installers and many are intimidated enough to not use the product.
Finally, the platform strike was never intended by its manufacturer to be a “finished” piece: it is always attached to a finished plate of a different shape. It takes a great deal of work to get the platform strike to look finished, and even then, the strike can only be made in two architectural finishes.
The other device, i.e. the Panicloc device, is an adaptation of a fail-safe solenoid powered bolt lock which mounts in a door header. It has a bolt that extends into a pocket installed in the top of a door by the application of electric current through a solenoid via a 90-degree lever. The Panicloc device utilizes the solenoid and lever system with a metal bolt that has a bevel on one side which extends into the latch. This device is not currently being made because it doesn't work well in this application.
There is one other device that is used to electronically control these doors, and that is the magnetic lock. However, since an electromagnetic lock requires that the mechanical exit device be removed from the door, this is not a preferred solution. Normal egress is disrupted. Normal access by key is lost. Additionally, in the event of a power failure, the door with a magnetic lock will be totally unlocked and unsecured. Many Fire Chiefs and Building Inspectors do not allow magnetic locks to be used on exit doors.
There is thus a need for an electric strike which can accommodate more mounting applications and is easier to install. It is desirable for the strike to be configured easily by the user to operate in either the “fail-safe” or the “fail-secure” mode.